1. Field of the Invention
The present invention relates to an apparatus for measuring the flatness of an outer lead of an integrated circuit package and in particular to an apparatus for measuring the flatness of an outer lead of a tape carrier package (hereinafter abbreviated as TCP).
2. Description of the Prior Art
In such a prior art lead flatness measuring apparatus, as shown in FIG. 1, a TCP 70 which has been positioned on an X-Y stage 71 has been observed from an upper position by a microscope 65. When the TCP 70 is focussed, the position of a lens-barrel of the microscope 65 is detected by a linear scale 66 and is converted by a Z decoder 67 into a numerical value representative of the distance between the front end of an objective lens and the surface of an observed outer lead 72, i.e. one of Data Points 61 as shown in FIG. 2. Similar measurements are repeated by driving the X-Y stage 71 along the outer lead 72 and recording the numerical values indicated by X, Y and Z decoders 69, 68 and 67 so that a plurality of measurement values which are necessary to recognize the outer shape of the outer lead 72, i.e. all the Data Points 61 in FIG. 2, are determined.
A regression line, i.e. a Line 1, of the Data Points 61, a Line 2 which is parallel with the Line 1, passes through any of the Data Points 61 and is farthest in an upward direction from the Line 1, and a Line 3 which is parallel with the Line 1, passes through any of the Data Points 61 and is farthest in a downward direction from the Line 1 are calculated by manual operation of these Data Points 61. Lead flatness 93 is obtained by calculating the distance between the Lines 2 and 3.
Such measurement and operation are performed for each of all the outer leads 72 on the TCP 70 to determine the flatness 93 of each outer lead 72. The Max. Point 62 and the Min. Point 63 among the Data Points 61 which the Lines 2 and 3 pass, respectively, are recorded for each outer lead. The maximum Max. Point 62 and the minimum Min. Point 63 among the Max. Points and Min. Points thus obtained, respectively, are determined for each side of the TCP 70, and the difference therebetween is determined as the flatness of a side.
Since a person manually carries out the measurement in the prior art lead flatness measuring apparatus shown in FIG. 1, it takes an average of two minutes to measure one Data Point. Since at least 50 Data points are needed to determine the flatness of one outer lead 72, 100 minutes is necessary per one outer lead 72.
In the case that the TCP 70 has, for example, at least 100 outer leads 72, it takes not less than 10,000 minutes, i.e. about 167 hours (7 days) to determine the flatnesses of 4 sides.
There are problems that an increase in the number of examination steps in a fabricating process of the TCP directly causes an increase in price of TCP and indirectly induces extension of period of time of delivery to customers. There is also a problem that, since measurement is performed with eyes of human being through the microscope 65, the measured values vary widely from one measuring person to the other and thus the reliability on the measured values is low.